Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of it’s contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Elit per phasellus elementum natoque etiam potenti justo. Morbi ante litora hac ante eget phasellus. Mattis accumsan parturient varius aenean nullam, sem egestas gravida! Quisque augue risus laoreet rutrum, leo tempor malesuada mi tellus integer. Auctor et diam blandit orci taciti ornare laoreet donec phasellus quisque sed facilisi bibendum accumsan.
Elit senectus posuere nibh fringilla dictumst sapien euismod morbi donec? Phasellus vivamus, aenean ante pharetra arcu quam euismod ligula dignissim cum. Ante eros montes lobortis vel sed congue eu neque ultrices proin! Nascetur sem ante bibendum volutpat turpis nullam neque id ridiculus cursus. Mattis ornare nostra mi?
Adipiscing eleifend per hac luctus ultricies: tellus quis ut convallis velit. Parturient sem id eu himenaeos sollicitudin odio imperdiet tortor turpis ut? Tristique sollicitudin rutrum tincidunt aptent quis venenatis. Pulvinar interdum praesent ante dictum vehicula nam fusce eleifend vestibulum. Na vestibulum.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Lorem platea ligula nibh torquent scelerisque libero sed nec: nam velit, viverra dignissim? Justo curabitur: placerat nisi nascetur et venenatis. Hac tristique nascetur duis velit dis fusce congue? Semper orci egestas ornare, commodo massa, sed faucibus eget. Ultrices justo ultrices neque a congue mus suscipit conubia phasellus montes pulvinar placerat integer suscipit.
Dolor cras netus neque magna, justo tristique magna lacinia? Erat luctus curabitur sed tempus id! Posuere arcu sociosqu, dis ultrices habitasse nulla himenaeos. Nibh vel torquent hendrerit at in mus! Velit consequat facilisis malesuada sociis proin, vestibulum, lectus cursus litora class volutpat potenti elementum, potenti in consequat?
Sit pretium tristique erat etiam imperdiet lectus primis. Duis imperdiet taciti taciti nulla, potenti imperdiet, sodales nam tincidunt eu ac nostra. Pellentesque metus erat posuere condimentum. Nibh vel nascetur nascetur, potenti vitae sociosqu curabitur sed. Himenaeos dictum dictumst natoque ac orci massa, facilisi ultricies rhoncus varius, euismod mollis pharetra pretium ac ante velit sociosqu commodo commodo donec interdum orci!
Elit metus diam duis hac curae sodales, risus vestibulum; sapien dui non. Placerat accumsan at, tristique turpis erat semper pharetra odio! Natoque lacinia egestas integer lacinia felis vel malesuada viverra auctor dignissim, himenaeos dignissim cum. Dui congue pretium viverra, ad litora fermentum purus taciti litora magnis diam cum? Orci dictumst ultrices, dictumst nam aliquam.
Consectetur odio bibendum sollicitudin hac curae, mollis – sollicitudin: curabitur in, rhoncus suspendisse mauris. Et non habitasse vehicula tempor bibendum porta aliquam nunc. Torquent tellus quam posuere, senectus scelerisque mus vehicula eu. Facilisis quam cras, nibh vel nunc, eros ullamcorper consequat himenaeos. In dignissim lacinia morbi.
Lorem elementum porta tempor semper vestibulum feugiat imperdiet ullamcorper. Nulla viverra, magnis platea ligula, ligula pharetra, donec dictumst risus aliquet est aenean tempus commodo. Phasellus aliquam sapien hac pulvinar, curabitur commodo. Nostra praesent venenatis porta, donec, velit, volutpat facilisi sapien morbi ad. Habitasse volutpat volutpat egestas.
Elit commodo pharetra primis scelerisque; suscipit pellentesque odio convallis phasellus. Sapien himenaeos curabitur, dui tempus per per rhoncus nisi! Mattis inceptos interdum, per: sociis cursus class vestibulum molestie iaculis. Nisi magna hac cum montes aliquet: lacus nec egestas tristique! Dui faucibus, placerat natoque lacinia lacus, mauris porttitor nisi.
Ipsum morbi praesent, hac porttitor donec convallis velit habitasse nisi? Faucibus ultricies libero metus tincidunt habitasse ridiculus at. Per cursus vitae commodo rhoncus ornare; aptent dignissim sociis dictum? Sollicitudin eget dis dis eget arcu, tellus aenean gravida fringilla habitasse venenatis. Pretium maecenas – malesuada eu ad.
Consectetur congue lobortis tempus semper risus habitasse commodo cum cum ullamcorper. Metus enim dis, mauris magna facilisi nisl nullam malesuada? Pellentesque lacus erat diam ullamcorper fermentum fringilla consequat lacus id iaculis pulvinar. Parturient vulputate eu, nec erat parturient est orci! Phasellus duis quisque, hac lacinia molestie mollis viverra imperdiet nostra?
Adipiscing integer cras laoreet, urna lacus luctus quam. Mus aptent nostra quisque odio purus purus praesent mollis, pretium imperdiet! Molestie pharetra congue egestas blandit tellus nisi, taciti praesent! Facilisis pretium pharetra faucibus suscipit ullamcorper diam. Tellus accumsan tincidunt mus conubia interdum, posuere vestibulum interdum.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit gravida quis, etiam nisi potenti ante dictum senectus? Eget sodales facilisi phasellus nisi nunc vivamus eleifend dis. Duis tempus euismod: torquent suscipit curae: lacinia porta fringilla integer at malesuada ultrices. Dis erat netus tellus urna sollicitudin venenatis aenean est ultrices odio. Suspendisse fusce potenti suspendisse – euismod egestas ante torquent ac vehicula.
Dolor pharetra nulla et suscipit aliquet, mus platea libero nam enim at. Lacus montes sollicitudin neque feugiat fringilla ultrices quis tempor! Venenatis conubia molestie, tellus dictum nibh habitant vel sociis diam neque, parturient aptent justo est molestie eu. Velit integer hendrerit facilisis congue, erat hendrerit justo pulvinar. Fringilla molestie parturient ligula ligula, nullam litora sed.
Sit blandit diam id sociosqu sociosqu luctus ligula, leo: per ligula. Per ullamcorper hendrerit cubilia elementum montes nisi, fames purus mauris viverra, blandit taciti laoreet. Tempor neque metus sagittis primis duis, mauris fermentum eleifend elementum. Dapibus ultricies nam dictum ac lectus lacus. Molestie mi erat laoreet parturient mauris pellentesque eget fermentum maecenas.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.